The safe operation of aircraft is heavily dependent on the experience and skill of the pilot. However, even for a highly experienced pilot, aviation can be a dangerous activity for crew and passengers alike.
A particularly perilous scenario occurs upon depressurization of the cabin at altitudes where the partial pressure of oxygen is not sufficiently high so as to provide the pilot with sufficient oxygen for normal functioning. In particular, a slow depressurization may not be noticed by the pilot, and hypoxia can set in insidiously. Early recognition of hypoxia is critical in preventing incapacitation to enable corrective actions to be taken. Sudden explosive decompression is self-evident but hypoxic symptoms from slow or unrecognised depressurisation are often subtle and may be difficult to recognise without previous training. Depending upon the altitude, there is often very limited time for aircrew to recognise any hypoxia symptoms before losing consciousness.
Hypoxia is a condition of reduced oxygen bio-availability caused by decreased oxygen diffusion from the lungs to blood, impaired oxygen transport in blood, decreased tissue perfusion or chemical toxicity in cells. At altitude decreasing barometric pressure leads to a decreasing partial pressure of oxygen in the air, which reduces the force driving oxygen from the lungs into the bloodstream. Hypoxia triggers various cardiovascular and respiratory adjustments in the body, but despite such compensations it causes impaired function in vision, cognition, motor control, and ultimately severe incapacitation, unconsciousness and ultimately death. At altitudes exceeding 20,000 feet consciousness can be lost rapidly, and this has been called the hypoxia “Critical Zone”.
The dangers of hypoxia in aviation have been clearly demonstrated numerous times, with one example being the crash of the Helios Airways Boeing 737-300 into a mountain on 14 Aug. 2005, killing all 121 passengers and crew. An investigation implicated pilot hypoxia due to failure of the cabin to pressurize at takeoff. Another accident caused by decompression resulting in pilot hypoxia was the loss of a Learjet in 1999 over South Dakota, and that of a Beechcraft 200 Super Air King which impacted near Mt Isa, in Queensland Australia.
In November 2010, United States Air Force F-22 Raptor crashed in Alaska, killing the pilot. Investigations showed the cause to be related to oxygen deprivation of the pilot. In 2011 the Air Force grounded its entire F-22 fleet for four months due to problems with the aircraft's oxygen generating system. Further problems were noted in 2012, with pilots being forced to land after experiencing symptoms of oxygen deprivation. In total, oxygen deprivation has been reported in at least 12 separate incidents across the 187 strong F-22 fleet since its 2005 launch.
A recent Australian Transport Safety Bureau report on hypoxia and loss of cabin pressure describes 517 incidents in Australia between 1975 and 2006. Indeed, the risk of hypoxia in civilian aircraft may be increasing as the performance and flight envelope of civil registered aircraft expands.
Oxygen warning systems on aircraft may not provide adequate protection and can malfunction or be missed or ignored. The effects of gradually developing hypoxia are subtle and can occur insidiously. At 25,000 feet aviators have three-five minutes to recognise hypoxia and act and rescue themselves.
A number of training programs are offered in the aviation industry in an effort to assist pilots in detecting the first signs of hypoxia. Early recognition is important because the pilot is able to take advantage of a breathing apparatus and prevent any further decrease in cognition. However, many of these training programs are deficient, as evident from the numbers of hypoxia related incidents which are still seen in aviation.
It is an aspect of the present invention to overcome or alleviate a problem of the prior art by providing improved systems, methods and devices for hypoxic flight training.